350-501 MPLS and Segment Routing Practice Question
Which protocol is typically used to distribute MPLS labels between directly connected LSRs?
⚠ Common exam trap
Cisco often tests the distinction between label distribution protocols (LDP) and routing protocols (OSPF, BGP) or signaling protocols (RSVP), trapping candidates who confuse the role of RSVP-TE for traffic engineering with the basic label distribution function of LDP.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
LDP
LDP (Label Distribution Protocol) is the standard protocol used to distribute MPLS labels between directly connected LSRs (Label Switch Routers) in a non-traffic-engineered MPLS network. It operates by establishing LDP sessions over TCP (port 646) and exchanging label mappings for each FEC (Forwarding Equivalence Class) based on the underlying IGP routing table, enabling hop-by-hop label switching without requiring explicit path setup.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
LDP
Why this is correct
LDP is specifically designed to distribute labels for MPLS forwarding.
- ✗
RSVP
Why it's wrong here
RSVP is used for traffic engineering, not for general label distribution.
- ✗
BGP
Why it's wrong here
BGP distributes VPN labels and routes, but not for general MPLS labels.
- ✗
OSPF
Why it's wrong here
OSPF distributes routing information, not MPLS labels.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.